1. Field of the Invention
The present invention relates to a machine tool using a polishing belt, and more particularly to a belt grinding machine with a belt adjusting device.
2. Description of the Prior Art
Sand paper is the simplest, the most common and useful tool for grinding and polishing, however, in the past, the user always utilizes the sand paper to perform a grinding operation by hands directly, therefore, the planeness of the object to be ground is more likely to be influenced by the skill of the user, or even the goods will be deformed by overgrinding, for example, a surface which is expected to be a flat surface is finally ground into an arc-shaped surface.
Therefore, an electric grinding tool, such as, a grinding wheel machine and a belt grinding machine, is developed. The belt grinding machine comprises a grinding belt winding around two rollers and a motor for driving one of the rollers to rotate, and then the grinding belt rotates the other roller, so as to perform grinding operation.
However, the rotary shafts of the rollers must be parallel to each other, such that the belt can work normally without deviation. The problem is that the belt grinding machine is driven by motor, which inevitably will cause vibration during operation, on top of that, various kinds of external conditions, such as the influence of tension of the belt, will cause displacement of the rotating shafts and make them unparallel, resulting in the deviation of the belt. Hence, it requires an adjusting device to adjust the belt and the rollers.
Presently, a belt grinding machine with such an adjusting device, as shown in FIG. 1, usually comprises a housing A which has an open side and in which is disposed a supporting rack B. Both ends of the supporting rack B are formed with a gap B1, and the gaps B1 are located opposite to each other. Both ends of a rotating shaft C1 of a roller C are received in the gaps B1 of the supporting rack B. A belt D winds around the roller C. The adjusting device E is disposed on the supporting rack B and is provided with a positioning piece E1 and an adjusting rod E2. The positioning piece E1 is fixed to the supporting rack B and is located adjacent to one of the gaps B1 of the supporting rack B. One end of the adjusting rod E2 is defined with outer threads E21 to be threaded with the positioning piece E1, an axial direction of the adjusting rod E2 is vertical to that of the roller C, and the other end of the adjusting rod E2 is provided with a control handle E22.
Referring to FIG. 2, when the roller C deviates, it will affect the belt D winding around the roller C. The adjusting rod E2 can be moved relative to the positioning piece E1 simply by rotating the adjusting rod E2 with the control handle E22 due to the cooperation of the outer threads E21 of the adjusting rod E2 and the positioning piece E1, as shown in FIG. 3, so that the adjusting rod E2 can push the rotating shaft C1 of the roller C to move the roller C, thus adjusting the belt D.
Referring to FIGS. 1-3 again, during the adjustment operation, since the conventional mechanism is not provided with an outer cover for the sake of adjustment, the worker is likely to be caught by the roller C or the belt D by accidentally touching them at a high speed rotation, causing injury.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.